Process of classification and separation of material particles



March 18, 1941.' W|EGAND 2,235,305 PROCESS OF CLASSIFICATION AND SEPARATION OF MATERIAL PARTICLES Original Filed Dec. 3, 1934 ATTO NEYS passed Man -18, 1941 I PATENT OFFICE PROCESS OF CLASSIFICATION AND SEPARA- TION OF MATERIAL PARTICLES Edwin L Wiegand, Pittsburgh, Pa.

Continuation of application Serial No. 755,694,

a December 8, 1934.

1939, Serial No- 282,808

This application July 4,

28 Claims. (c1; 209-127) This application is a continuation of my copending application 755,694, filed December 3, 1934.

My invention relates to classification and sepa- 5 ration of material particles, and the principal object of my invention is the provision of an improved process of classification and separation of material particles. My invention finds one appli-, cation in the manufacture of refractory heatconducting electrical insulating material, as for use in, electrical resistance heating elements wherein the resistor is refractory embedded, but my invention is not limited to this particular application.

In the manufacture of refractory electrical insulating material I have found that the commlngling of particles of difierent electrical resistivity is likely to reduce the electrical resistivity of the aggregate below the average value, and that the removal of the particles of lower electrical resistivity results not only in increase in resistivity of the residue, but in decrease in variation in resistivity between diflerent portions or specimens of the residue, andfor these and other reasons I deem it' important in themanufacture of refractory electrical insulating material that the particles of lower resistivity be removed.

At least as respects the materials with which I have operated, in general those particles that are particularly susceptible to electromagnetic infinance are of relatively low electrical resistivity, but the reverse does not obtain, that is, only part of the particles of relatively low electrical resis- 'tivity are particularly susceptible to magneticinfiuence, and accordingly, I have not found it possible to attain any such elimination of the par ticles of relatively low resistivity as I consider satisfactory, merely by magneticclassification. and-separation.

a At the same time,inasmuch as all or almost all of the'particles segregated'by magnetic classification and separation are. particles of relatively low electrical resistivity that need to be eliminated, so that magnetic; classification and separation eliminates few if any particles that are desirable in such refractory ,electrical insulating material, in practicing my invention with relation to refractory electrical insulating material I may employ magnetic classification and separation as a preliminary step, to remove a considerable part of the undesirable particles in this way.

In an endeavor to remove the remainingparticles of relatively low resistivity I have subjected the residue from the magnetic classification and separation to electrostatic classification and separation. Speaking generally, the susceptibility of a particle to electrostatic influence is proportional to the electrostatic capacity of the particle, and electrostatic capacity is greater in par- 5 ticles of relatively higher conductivity and less in particles of relatively lower conductivity, or applied to the material on' which I have operated, greater in particles of relatively lower resistivity and less in particles of relatively higher resistivlty. Therefore it would be expected that electrostatic classification and separation would eliminate a considerable portion of the remaining particles of relatively low resistivity.

In carrying out this electrostatic classification and separation I have warmed the material suillciently to drive of! mechanically associated moisture, for example, up to temperatures of approximately 250 F., and in this way have eliminated erratic variations and uncertainties that otherwise would be occasioned by the presence of such moisture, and with this precaution I have found that this low-temperature electrostatic classification and separation is moderately beneficial, for instance in material employed in heating elements wherein the material may be brought to temperatures of say up to perhaps 1300 F. I have found, however, that by superheating the material, for example, to approximately 800 F., and conducting an electrostatic classification and separation while the material is at this supertemperature, I attain marked improvement over the results attained by only the cold electrostatic classification and separation.

I have found that the various kinds of particles generally possess different resistivities at the temperature of the cold electrostatic classification, but that at this cold temperature the resistivity of each of the different kinds of particles. is so extremely high that the diiferences are relatively small. I have found also that each kindoi' par-v ticles'has a difi'erent and usually lower resistivity at high temperatures, and further, that the various kinds of particles have diiferent rates of change in resistivity with change in temperature.

'In fact, I have found that these conditions obtain even among different particles of the same kind, due apparently to slight variations in physical or chemical structure, or to other reasons not so definitely ascertainable.

Under the circumstances I believe the improvemerit resulting from theme-electrostatic classiflcation and se ration may be ascribed in part to the fact that t e particles are subjected to the treatment at a temperature at which the resiss5 lower resistivity either cold or hot.

tivities have decreased sumciently that differences in electrostatic susceptibility have become sufiiciently pronounced to permit accurate separation based thereon, and accordingly, thatthe use of elevated temperatures is beneficial in itself. However, undoubtedly a very substantial part of the improvement results from effecting the classification and separation at a temperature so approximating the temperature at which the material is to be employed that'the classification and separation actually segregates those particles that will have low resistivity at the temperature at which the material is to be employed.

Obviously, under these circumstances successive electrostatic classification and separation at different temperatures is of increased advantage as segregating those particles possessing Also, in this respect I have found that by successive electrostatic classification and separation at different temperatures, I may effect separations not possible at either temperature.

For example, with three values of particles, one of relatively high resistivity both hot and super-hot, a second of relatively high resistivity hot butof relatively low resistivity super-hot, and a third of relatively low resistivity both hot and super-hot, I may segregate the third value by hot electrostatic classification and separation, and then may segregate the second by subjecting the residue of the hot electrostatic classification and separation to super-hot electrostatic classification and separation, leaving the first also segregated as the residue of the super-hot electrostatic classification and separation. I have found, therefore, that by reason of the differences in rate of change of resistivity, by successive electrostatic classification and separation at different temperatures, I may segregate particles not capable of segregation at either temperature, or for that matter, at any single temperature. 4

Owing to the wide variety of materials to which my process is applicable it is impossible to set exact temperatures, electrical potentials, or other conditions, for general application, but the treatment of an ore of zircon (ZrSiOd may be taken by way of example.

A residue of such ore analyzing 210: 60% or higher and S10: 40% or lower possesses a relatively high fusing point, a relatively high electrical resistivity, and a relatively low rate of decrease in resistivity at least up to temperatures of approximately 1300 F., and at the same time possesses moderately high heat conductivity, and accordingly such residue is peculiarly adapted for use as a refractory material for embedding the resistors of electrical resistance heating elements operating at temperatures now employed. However, such residue does not occur pure, but in an ore containing in addition to the grosser impuriaaaasos substantially only with these other minerals, principally ilmenite, rutile, magnetite, and sometimes monazite.

The iron-bearing minerals either are or may be made susceptible to magnetic. influence, accordingly I prefer to eliminate the magnetite and ilmenite by magnetic classification and separation. However, the rutile and monazite are relatively less susceptible to magnetic influence,

and also; at low temperatures rutile and mona-' nate the rutile by electrostatic classification and separation at a temperature somewhat in excess of 600 It, for example, 800 F'., Also, that I may eliminate the monazite in the same way. at a temperature depending on the composition.

I Specifically, I have found ,that such zircon ore subjected only to preliminary treatment and magnetic classification and separation may have resistivities of, for example, at 1100 F., 20.0 megohms, at 1200 F., 14.0 megohms, and at 1300" F., 6.5 megohms, while the same material subjectcd also to cold electrostatic classification and separation will be only of slightly increased resistivity. for example, at 1100 F., 24.3 megohms, at 1200 F., 15.0 megohms, and at 1300 F., 7.2 megohms, but that treatment of the same material by electrostatic classification and separation at approximately 800 F. 'renders the material of markedly increased,resistivlty, for example, at 1100 1.', in excess of 50.0 megohms,

at 1200 F., 21.7 megohms, and at 1300" F., 10.0

On the other hand, if the same material is heated to and tested at a temperature of approximately 1600 F., the results may be reversed. The material subjected only to preliminary treatment and magnetic classification and separation may have a resistivity of say 0.93 megohm, the material subjected also to cold electrostatic classification and separation a resistivity of only 0.64 megohm, and the material subjected also to electrostatic classification and separation at approximately 800 F., a resistivity of only 0.43 megohm.

It appears, then, that while thermo-electrostatic classification and separation is advantageous in itself, as acting at a temperature at which the differences in resistivity generally have become more pronounced, and that while successive electrostatic classification and separa-' tion at difi'erent temperatures is advantageous and can be employed to segregate particles not otherwise separable, nevertheless, in treating to secure a residue of maximum electrical resistivity, the electrostatic classification and separation, or

the successive electrostatic classifications and separations, desirably should include the range of temperature to which the refractory is to be subjected, including if possible themaximum temperature to which the refractory is to be subjeoted, at least to an extent to include whatever decisive critical points may be within the rang Specifically. material )ntended to be used at 1600 F. should be subjected to electrostatic classification and separation at a temperature sumciently approximating 1600 F. that no decisive critical point lies between.

My process, therefore, contemplates thermoelectrostatic classification and separation-at elevated temperatures at which the diiferences in electrostatic susceptibilities of the particles are sumciently pronounced to form a suitable basis for electrostatic classification and separation, rather than at the low temperatures required merely for drying the material, at which the electrostatic susceptibilitiesof the particles are too slight and/or the diiferences in electrostaticsusceptibility relatively insumcient.

My process also contemplates successive electrostatic classifications and separations at different temperatures, higher or lower, to eliminate particles having low resistivity at any of the selected temperatures, and the selection of the temperatures to approximate as largely as practicable the range of temperatures within which the material is to be employed.

My process contemplates also electrostatic classification and separation at an elevated temperature sum'ciently close to the temperature at which the material is to be used that the selection is efi'ective for the temperature of use.

Additionally, my invention comprises the use of electrostatic classiflcationand separation at one or more elevated temperatures selected'to effeet the particular segregation sought to "be effected, based on difference in rate of change of resistivity with change in temperature.

However, once a material is separated into its constituents, obviously the constituents may be employed for any and all purposes for which they may be suitable, accordingly-my'proces's is valu-- able not only in the production of material for purposes where the degree of electrical resistivity or conductivity is important in itself, but also in the production of materials for other purposes. It is applicable likewise to the production of 'material that is electrically conductive and to the production of material that is electrically resistant or electrically insulating, to the production of material that is heat-insulating and to the production of material that is heat-conduct ing, and'to the production of non-refractory material and to the production of refractory material.

Also, while my invention is particularly valuable as applied to the production of materials for uses where electrical resistivity or conductivity is directly important, italso is applicable with particular facility in the production of materials in respect of which the fundamental criterionds a property that bears some direct relation to electrostatic susceptibility or electrical resistivity or conductivity. For example, while not all inaterials that suifer a rapid lowering of resistivity with increase in temperature are fusible at relatively low temperature, most if not all mineral materials sufier a heavy decrease in electrical retion therefore is extremely valuable both for di rect classification on the basis of electrostatic susceptibility or electrical resistivity and for indirect classification on the basis of fusing point, and therefore contributes both to the electrical art and-to the refractory and ceramic arts, particularlyi in connection with super-refractories and super-insulators, and in an especially particular sense, in connection with the manufacture of refractory insulators normally operating at 5 more or less elevated temperatures.

In performing my process, particularly as applied to free flowing material, I may-conveniently employ apparatus such as is disclosed in the accompanying drawing, in which the single figure 10 is 'a general vertical sectional view.

The illustrated apparatus comprises a base ll provided with a central boss l2 having an axial I screw-threaded aperture I3 in which is received the screw-threaded lower end H of a supporting 15 stud l5 provided with an alined upper end terminating in a. concentric cone It on which seats the conically recessed lower end of a coaxial shaft H. The shaft I'I may be raised and lowered by rotation of the stud 15, as by means of the hand- 20 wheel l8, and the stud may be locked in any adjusted position by means of the hand lock-nut, I9, thus locking the shaft IT in corresponding vertical-adjusted position. The shaft I! is supported laterally by a bearing bracket 20 suitably mount- 25 edonthebasell.

' Mounted on the upper end of the shaft i1 is a feed duct 2| provided internally with a spider 22 having a central screw-threaded aperture 23 cooperatively receiving a. reduced screw-threadedextension 24 of the shaft I1, whereby the feedduct 2| is supported on the shaft H, but vertically adjustable by rotation relative to the shaft ll. Available to lock the feed duct 2| in any adjusted positionis a lock-nut 251 formed conical 35 on its upper side to minimizelodgment of material thereon.

herein I have shown the cone 26jas of lower in- 45 rate of discharge, merely by change in rate or inclination, and the shaft ll aspr'ovided with agitating means 28, operative toagitate the shaft I! and cone 26 to efiect discharge of the material from the cone 26, and for free-flowing par- 50 ticles I preferthis arrangement, both because it 1 provides greater uniformity of discharge and also because it permits convenient adjustment of the: tensity of agitation of the shaft I1 and cone 26.;

The agitator 28may be an electro-magnetic E65 vibrator agitating the shaft i1 and cone 26 either axially of the shaft IT or about the axis of the shaft ll, or may be an electric motor rotating the shaft l1 and cone 26 and acting in conjunction with cooperating surfaces that produce concur- 0 rent vibration of the shaft l1 and cone 26, or' the agitator-28 may be of any other construction that may be found desirable for any particular reason or for any particular material or use. A

I movement about the axis of the shaft 11 in some sistivity as the fusing point is approached, ac-

instances has the advantageof breaking any wedging of material particles between the cone 26 and any other part, such as the gate 29 hereinafter described, but-any such movement needs to be agitation as distinguished from rotation at 7 any speed that will impart to the particles any measurable centrifugal force or otherwise will interfere with the desired condition of the particles leaving the periphery of the cone 26 in a uniform stream and with a minimum velocity 75 incapable of introducing any variable into the operation of the apparatus.

Above the cone 23, slightly inwardly of the periphery 21, isvan annular gate 23 provided to afford additional-control of the discharge from the cone 23 and mounted vertically-adjustable by means of a plurality of rods 33 secured to the upper face of the gate 23 and provided with screw-threaded upper ends 3| passing through plain apertures 32 in a spider 33 supported by a frame 34 secured to and rising from the base I I, the gate 33 being secured in vertically adjusted position by nuts 33 screw-threadedly engaging the screw-threaded upper ends 3| of the rods 33 and abutting the upper and lower faces of the spider 33.

Positioned above the feed duct 2| is a furnace 33 provided with a discharge spout 31 extending into the feed duct 2| to be self-stopping, that is, when material builds up in the feed duct 2| to adjacent the level of the end of the discharge spout 31 the material in the feed duct 2| will automatically block the discharge spout 31 and prevent .further discharge of material into the feed duct 2| until the level of the material in the feed duct 2| has been suitably lowered.

The furnace 33 may be heated in any suitable manner, depending largely on the temperature desired and the sources available, and preferably is provided with temperature control and automatic temperature limitation; herein I have illustrated a furnace for moderate temperatures, and have shown the furnace heated by electric resistance heating elements 33 energized from a suitable sll ply. Also, I have shown the feed duct 2| heated by similar elements 33, the cone 23 by other elements 33, and the gate 23 by further elements 4|, and have shown the upper end of the gate 23 closed by a cover 42 mounted on the feed tube 2| and heated by a further heating element 33, all to maintain the material at the desired temperature in the hopper 3| formed by the'cone 23, gate 23, and cover 42, the various heating elements to this end being under suitable control.

In operation, the material is heated in the furnace 33,'passes from the furnace 33 through the spout 31 into the feed duct 2|, and from the feed duct 2| onto the cone 23 down and from the peripheryv 21 of which 'it travels under the impetus of the agitation effected by the agitator 23, falling from the cone periphery 21 in an annular stream preferably of'nniforrn and minimum velocity. The flow from the furnace 33 into the feed duct 2| is regulated by the blocking of the furnace nozzle 31 when the level of the material in the feed duct 2| rises above a predetermined maximum, while the rate of flow from the feed duct 2| onto the cone 23 is regulated by the vertical position of the vertically adjustable feed duct 2| and to some extent by the rate and intensity of action of the agitator 23. Likewise, the rate of flow from the cone periphery 21 is regulated by the vertical position of the vertically adjustable gate 23 and by the rate and intensity of action of the agitatorj23. Desirably the parts cover 42, and for this purpose the cover 32 may be provided on its inner surface with a heat-insulating surfacing 43, and likewise, the gate 23 may be provided on its exterior surface with an electrical-insulating heat-insulating covering 44.

Spaced from the cone periphery 21, adjustable relative thereto, is an annular electrode 43 supported. indirectly by the base l, but suitably insulated from the other parts of the machine, and connected to this electrode 43 is the-positive terminal of a variable-potential unidirectional electric circuit of, for example, from 1000 to 50,000

to the remainder of the machine, and particularly to the cone 23 and the gate 29.

The material in passing over the cone 23 will acquire a negative charge, varying in intensity with each particle according to the electrostatic capacity of the particle, and when the particle leaves the cone periphery 21 the particle will be deflectedv outwardly by the annular positive electrode 43 according to the strength of the negative charge the particle has acquired. Some particles will acquire little or no charge, will be influenced little or not at all, and will drop into the-inner annular receptacle 43. Other particles will acquire an intermediate charge, will be influenced 'volts, the negative terminal of which is connected intermediately, and will'fall in an intermediate annular receptacle 41. Still other particles will acquire a strong charge, will be influenced strongly, and will fall in an outer annular receptacle 43.

Each of the receptacles 43-41-43 is of progressively increasing depth from a shallow place- 43 in both directions to a diametrically opposite deep place 33 at which the receptacle is provided with a suitable discharge spout 3| through which the material from that receptacle is discharged, as into a suitable container 32. The receptacles 43-41-43 are supported on the frame 34, and the outer wall of the outer receptacle 43 is extended upwardly and carries a plurality of brackets 33 formed of insulating material and mountin the annular electrode 43.

As will be appreciated. the relative elevations of the cone 23 and of the electrode 43 may. be

"adjusted by raising or lowering the electrode 43,

or by raising or lowering the cone .23 by raising or lowering the shaft l1 by means of the hand-nut l3, and the electrode 43 may be replaced by an electrode of any other diameter, all to properly adjust the position, shape, and intensity, of the electrostatic field.

It is desirable, however. that provision be made whereby the division of the material between the receptacles 43-41-43 may be varied, and for this purpose the divisions between the receptacles 43 and 41, and between the receptacles 41 and 33, are constituted by annular members 34 and 33 provided with sharp upper edges 33 and with depending skirts 33 embracing the respective receptacle edges but mounted on the frame 34 independently of the receptacles and vertically movable relative thereto. For this purpose the frame 34 is provided with two raising and lowering mechanisms 31 operating two brackets 33 to which the two members 34 and 33 are secured. It will be appreciated that the higher the member 34 or 33 the greater the deflection required for the particle to pass over the member, and accordingly, that changes in the division of the material may readily be accomplished by raising or lowering the members 34 and 33.

It also will be appreciated that the particular apparatus herein disclosed eliminates any variation byreason of centrifugal action, since with any indicated construction of the agitator 23, the

minimum velocity, without in -any sense being thrown. The various parts of the apparatus subjected to heat are made of materials suitably heat-resistant. Also, the division of the particles may be into three parts as indicated, or into any other number 01' parts as may be desired, either more or less, and the number of receptacles 4641-48, annular members 54 and 55, supporting brackets 58, and raising and lowering mechanisms 51, will be increased or decreased accordingly.

On the other hand, it will be appreciated also that my processes are in no way limited to the particular apparatus herein disclosed, and that while I regard this apparatus as particularly sat- I cate. The term nature refers to the qualities or characteristics of a particle which distinguish that particle from any other particle, and whether the particles are of different species or kinds or of the same species or kind. The term normal temperatures designates ordinary temperatures, for example, in the neighborhood of 70 F. Reference to driving off mechanically associated moisture, and the term dry condition, refer to a condition in which mechanically associated moisture is not present in any amount sufficient to control or change the essential result of the separation. Also, in any instance there may be present particles other than those particularly considered, and the classification and separation may place such other particles with one part of the particles particularly considered, or, divided between two or more such parts, or separately from any such parts. And in general, it is to be unmixture of said particles to a super-temperature above such drying temperature, said super-temperature approximating the fusing temperature of a selected class of said particles, to occasion a substantial change in an electrical characteristic of said particles, and, by causing said superheated mixture to move with respect to an electrostatic field, eflecting a separation from said mixture of said selected class of particles which is determined by the difierence in such electrical characteristic as possessed by said selected class of particles and by the other particles 01' said mixture at said super-temperature.

2. The process of classifying a mixture or dry particles of refractory materials of difierent natures, which comprises: super-heating said mixture to a super-temperature, above the temperature required to dry said particles and maintain said particles dry, said super-temperature being determined by the fusing temperature of a selected class of said particles; and causing said superheated mixture to move with respect to an electrostatic field and efiecting a separation from said mixture of said selected class of particles.

3. The process of fractionally classifying a mixture of dry material particles of difierent natures, which comprises: superheating said mixture to a super-temperature, above the temperature required to dry said particles and maintain said particles dry, at which super-temperature a substantial relative diiierence in the electrostatic susceptibility of a certain class of said particles with respect to another class of said particles exists, said super-temperature being determined by the difierences in nature of said different classes and by the'relatively dissimilar variability in response to temperature change of the electrostatic suspectibilities possessed by said different classes due to said differences in nature;

and causing said superheated mixture to move with respect to an electrostatic field and efiect ing a separation of said classes on the basis of the difference in electrostatic susceptibility of said classes at said super-temperature; and heating a selected class of particles, resulting from said separation, to a temperature difierent from said super-temperature; and causing said so heated selected class to move with respect to an electrostatic field and effecting a further separation of the particles of saidselected class on thebasis of the difierence in electrostatic susceptibility of sub-classes of particles of said selected class at said different temperature.

4. The process of fractionally classifying a mixture of dry particles of refractory materials of difierent natures, which comprises: superheating said mixture to a super-temperature, above the temperature required to dry said particles and maintain said particles dry, at which super-temperature a substantial relative diflerence in the electrostatic susceptibility of a certain class of said particles with respect to another class of said particles exists, said supertemperature being determined bythe difierence in nature or said diflerent classes and by the relatively dissimilar variability in response to temperature change of the electrostatic susceptibilities possessed by said difierent classes due to said difierences in nature; and causing said super-heated mixture to move with respect to an electrostatic field and efiecting a separation of said classes on the basis of the difierence in electrostatic susceptibility of said. classes at said super-temperature; and heating a selected class of particles, resulting from said separation, to a temperature diflerent from said super-temperature, and causing said so heated selected class to move with'respect to an electrostatic field and 'efiectinga further separation of the particles of said selected class on the basis of the difl'erence in electrostatic susceptibility of subclasses of particles of said selected class at said difierent temperature.

5. The process of effecting a desired separation of a mixture of dry material particles of different natures, comprising particles of refrac-- tory electrical insulating material, into a plurality of diiferent portions, to obtain a desired reiractoryelectrical insulating material, which comprises, heating said mixture to a selected super-temperature which is substantially above a drying temperature but below the temperature at which the desired separation would be prevented by agglomeration of the particles by fusion, which in effect/approximates the maxi mum temperature at which said refractory electrical insulating material is to be used, and at which the desired separation may be efiected by reason of the difierence in the motion response or the particles to an electrostatic field at that temperature, and subjecting said particles to the action of an electrostatic field while said particles are at said super-temperature, and effecting a separation of said particles at said supertemperature, by reason of said difference in said motion response at said super-temperature, to segregate said desired refractory electrical insulating material.

6. The processor efiecting a desired separa-- tion of a mixture or dry material particles of dif- Ierent natures, into a plurality of diflerent portions, which comprises, heating said mixture to a selected super-temperature which is substantially above a drying temperature but below the temperature at which the desired separation would be prevented by agglomeration of the particles by fusion, and at which the 'desired separation may be eflected by reason of the difierence in the motion response of the particles to an electrostatic field at that temperature, and subjecting said particles to the action of an electrostatic field while said particles are at said super-temperature, and efiecting a separation of said particles at said super-temperature by reason of said difference in said motion response at said super-temperature, and then subjecting a separated part of said particles to the action of an electrostatic field while said part or said particles is at a selected temperature diflerent from said selected super-temperature and at which a further separation may be eflected by reason of the diflerence in the motion response of the particles or said part to an electrostatic field at that diflerent temperature, and efi'ecting a separation of said particles 01 said part at said diflerent temperature, by reason of said diflerence insaid motion response at said difierent temperature.

'I. The process of efiecting a desired separation or a mixture or dry material particles of diflerent natures, into a plurality of diil'erent portions, which comprises, heating said mixture to a selected super-temperature which is substantially above a, drying temperature but below the temperature at which the .desired separation would be prevented by agglomeration oi the particles by fusion, and at which the desired separation may be effected by reason of the dirierence in the motion reponse oi the particles to an electrostatic field at that temperature, and subjecting said particles to the action otan electrostatic field while. said particles are at said super-temperature, and efiecting a separation or said particles at said super-temperature by reason of said diilerence in said motion response at said super-temperature, and then subjecting a separated part of said particles to the action of an electrostatic field while said part. or said particles is at a difierent selected super-temperature, also above a drying temperature but below the temperature at which the desired separation would be prevented by agglomeration of the particles by fusion, but difierent from the first said selected super-temperature and atwhich a fur:

ther separation may be eflected by reason of the diflerence in the motion response of the particles or said part to an electrostatic field at that different super-temperature, and. effecting a separation of said particles oi said part at said different super-temperature, by reason of said difi'erence in said motion response at said difierent super-temperature.

8. The method of effecting electrostatic separation of a mixture of dry material particles comprising refractory electrical insulating material, into at least two classes of pmticles, to obtain a desired electrical insulating material, comprising, differentially adjusting the electrostatic susceptibilities of said classes by bringingsaid mixture at least to a temperature which is substantially above a drying temperature and in eifect approximates the maximum temperature at which said desired material is to be used, and .at which there exists a substantial difference in electrostatic susceptibility between one part of the particles and another part oi the particles, subjecting said mixture to an electrostatic field'at said temperature, and efiecting a separation of said classes by reason of. the difierentially adjusted: electrostatic susceptibility existing at said temperature, to obtain said desired electrical insulating material.

9. In respect of a mixture of dry material particles, the process of eflecting'a' separation of said particles, separating said particles into a plurality of portions, which comprises, heating said particles at least toa first temperature which is substantially above normal temperatures, and at which there exists a substantial diflerence in motion response to an electrostatic field, between one part of said particles and another-part of said particles, by reason of which a desiredseparation of said particles may be effected, and while said particles are substantially at said first temperature, subjecting said particles to the action of an electrostatic field, and eflectiin'gv a separation separating said particles into said portions, by reason of said diflerence in m'otion response, and then, in respect of a separated fraction of said particles, causing the particles of said fraction to be at a second temperature, substantially diflerent from said first temperature-at which there exists a substantial diflerence in motion response to an electrostatic field, between one part of said particles of said fraction and another part of said particles of said fraction, by reason of which a desired separation of said particles of said fraction may be effected, and while said particles of said fraction are substantiallyat said second temperature, subjecting said particles of said fraction to the action or an electrostatic field, and eflecting a separation of said particles of said fraction into a plurality of portions, by reason of saidldifierence in motion response at said second temperature.

10. The process of separating into a plurality of portions, co-mingled particles of mineral material the electrostatic susceptibilities of which in dry condition at normal temperatures are of the same order of magnitude, which comprises, subjecting said particles to the action of an electrostatic field while said particles are of the same chemical constituencies as in dry condition at normal temperatures but are at a selected supertemperature above two hundredand fifty degrees Fahrenheit determined on the basis of differentiation in electrostatic susceptibility in response to change in temperature, and effecting a division of said particles into said portions, on-the basis 01' the electrostatic susceptibilities at said super-'- temperature, while said particles are of said same chemical constituencies.

11. The process 01 separating into a plurality of portions, co-mingled particles of refractory mineral material the electrostatic susceptibilities of which in dry condition at normal temperatures areof the same order of magnitude, which com- 5 prism, subjecting said particles to the action of an electrostatic field while said particles are .of the same chemical constituencies as in dry condition at normal temperatures but are at a selected super-temperature above two hundred and i fifty degrees Fahrenheit determined on the basis of differentiation in electrostatic susceptibility in response to change in temperature, and efiecting "a division of said particles into said portions, on the basis of the electrostatic susceptibilities at said l super-temperature, while said particles are of -said same chemical constituencies.

12. The process of separating into a plurality of portions, co-mingl'ed particles of mineral oxides or oxide compounds the electrostatic susceptibilities of which in dry condition at normal temperatures are .of the same order of magnitude,

which comprises, subjecting said particles to the action of an electrostatic field while said particles are of the same chemical constituencies as in dry condition at normal temperatures but are at a selected super-temperature above two hundred and fifty degrees Fahrenheit determined on the basis of difierentiation in electrostatic susceptibility in response to change intemperature, and

0 effecting a division of said particles into said portions, on the basis of the electrostatic susceptibilities at said super-temperature, while said particles are of said same chemical constituencies.

13. The process of separating into a plurality of portions, co-mingled particles of zircon ore the electrostatic susceptibilities of which in dry con dition at normal temperatures are of the same order of magnitude, which comprises, subjecting said particles to the action of an electrostatic field 40 while said particles are of the same chemical constituencies as in dry condition at normal tem peratures but are at a selected super-temperature above two hundred and fifty degrees Fahrenheit determined on the basis of difierentiation in electrostatic susceptibility in response to change in temperature, and effecting a division of saidpartieles into said portions, on the basis of the electrostatic susceptibilities at said super-temperature, while said particles are of said same chemical constituencies.

14. The process of separating into a plurality of portions, co-mingled particles of mineral material the electrostatic susceptibilities of which in dry condition at normal temperatures are of the same order of magnitude and low, which comprises, subjecting said particles to the action of an electrostatic field while said particles are of the same chemical constituencies as in dry condition at normal temperatures but are at a selected super-temperature above two hundred and fifty degrees Fahrenheit determined on the basis of difierentiation in electrostatic susceptbility in response to change in temperature, and effecting a division of said particles into said portions, on the basis-of the electrofiatic susceptibilities at said supentemperature, while said particles are of said same chemical constituencies.

15. The process of separating co-mingled particles of refractory mineral-material, segregating 7 particles suitable for use as electrical insulating material at elevated temperatures, which comprises, subjecting said particles in dry condition to the action of an electrostatic field while said particles are at a selected super-temperature above two hundred and fifty degrees Fahrenheit and not less than the minimum temperature which in effect approximates the maximum temperature to which it is intended said insulating material will be subjected in use but at which the particles to be segregated are of the same 6 chemical composition as in dry condition at normal temperatures, and eifecting a division of said particles on the basis of the electrostatic susceptibilities at said super-temperature.

16. The process of separating co-mingled par- 10 ticles of .refractory mineral material, segregating particlessuitable for use as electrical insullating material at elevated temperatures, which comprises, subjecting said particles in dry condition to the action of an electrostatic field while 15 said particles are at a selected super-temperature at which said particles are of the same chemical compositions as in dry condition at normal temperatures but which is above two hundred and fifty degrees Fahrenheit and not less than the 20 minimum temperature which in effect approximates the maximum temperature-to which it is intended said insulating material will be subjected in use, and efiecting a division of said particles on the basis of the electrostatic susceptibili- 25 ties at said super-temperature.

1'7.- The process of separating co-mingled particles of mineral material which comprises successive fractionations by successive subjections to the action of electrostatic field at substantially different temperatures at each of which exist substantial differences in electrostatic susceptibilities in dry condition by reason of which part of the separation may be efiected, said temperatures being determined on the basis of differentiation in electrostatic susceptibilities in response to change in temperature and the diifer ences in electrostatic susceptibilities being materially diiferent at the difi'erent temperatures, including, subjecting said particles indry condi- 40 tion to the action of an electrostatic field whilesaid particles are at one such temperature, and eifecting a division .of said particles on the basis of the electrostatic susceptibilities thereof at that temperature, and then subjecting a fraction of 45 said particles the electrostatic susceptibilities whereof in dry condition at said one temperature were of the same order of magnitude, in dry condition to the action of an electrostatic field while those particles are of the same chemical con-, 50 stituencles as when previously subjected but are at another such temperature, and effecting a.- division of those particles on the basis of the electrostatic susceptibilities thereof at that temperature. 55

18. The process of separating co-mingled particles of refractory mineral material which comprises successive fractionations by successive subiections to the action of electrostatic field at substantially difi'ere'nt temperatures at each of m which exist substantial differences in electrostatic susceptibilities. in dry condition by reason of which part of the separation may be efiected, said temsubjections tothe action of electrostatic field at substantially different temperatures at eachof which existsubstantial differences in electrostatic susceptibilities in,dry"condition by reason of which part of the separation may be effected, said temperatures being determined on the basis of differentiation in electrostatic susceptibilities in response to change in temperature and the dif-- ferences in electrostatic susceptibilities being materially different; at the different temperatures, including, subjecting said particles in dry condition to the action of an electrostatic field while said particles are; at one such temperature, and effecting a division of said particles on the basis of the electrostatic susceptibilities thereof at that temperature,- and then subjecting afraction of said particles the electrostatic susceptibilities whereof in'dry condition at said one temperature were of the same order of magnitude, in dry condition to the action of an electrostatic field while those particles are of the same chemical constituencies as when previously subjected but are at another such temperature, and effecting a division of those particles on the basis of the electrostatic susceptibilities thereof at that temperature.

20. The process. of separating co-mingled particles of zircon ore which comprises successive fractionations by successive subjections to the action of electrostatic field at substantially different temperatures at each of which exist substantial differences in electrostatic susceptibilities in dry condition by reason of which part of the separation may be effected, said tempera tures being determined on the basis of differentiation in electrostatic susceptibilities in response to change in temperature and the differences in electrostatic susceptibilities being materially dif-,

ferent at the different temperatures, including, subjecting said particles in dry condition to the action of an electrostatic field while said par-- ticles are at one such temperature, and affecting a division of said particles on the basis of the electrostatic susceptibilities thereof at that temperature, and then subjecting a fraction of said particles the electrostatic susceptibilities whereof in dry condition at said one temperature were of the same order of magnitude, in dry condition to the action of an electrostatic field while those particles are of ,the same chemical constituencies as when previously subjected but are at another such temperature, andeffecting a division of tion may be effected, said temperatures being determined on the basis ofdiiferentlation in electrostatic susceptibilities in response to change in temperature and the differences in electrostatic susceptibilities being materially different at the dlflerent'temperatures, including, subjecting said particles in dry condition to the action of an electrostatic field while said particles are at one such temperature, and effecting a division of said particles on the basis of the electrostatic susceptibllities thereof atthat temperature, and then subjecting a fraction of said particles the electrostatic susceptibilities whereof in dry condition at said one temperature were of the same order of magnitude, in dry condition to the action of an electrostatic field while those particles are of the same chemical constituencies as when previously subjected but are at another such temperature, and effecting a division of those particles on the basis of the electrostatic susceptibilities thereof at that temperature.

22. The process of separating co-mingled particles of refractory mineral material which comprises successive fractionations by successive subjections to the action of electrostatic field at substantially different temperatures at least one of which is above two hundred and fifty degrees Fahrenheit, at each of which exist substantial differences in electrostatic susceptibilities in dry condition by reason of which part of the separation may be effected. said-temperatures being determined on the basis of differentiation in electrostatic susceptibilities in response :to change in temperature and the diflerences in electrostatic susceptibilities being materially different at the different temperatures, including, subjecting said particles in dry condition to the action of an electrostatic field while said particles are at one such temperature, and effecting a division of said particles on the basis of the electrostatic susceptibilities thereof at that temperature, and then subjecting a fraction of said particles the electrostatic susceptibilities whereof in dry condition at said one temperature were of the same order of magnitude, in dry condition to the action of an electrostatic field while those particles are ofthe same chemical constituenciesas when previously subjected but are at another such temperature, and effecting a division of those particles on the basis of the electrostatic susceptibili'ties thereof at that temperature.

23. The process of separating co-mingled particles of zircon ore which comprises successive .fractionations by-successive subjections to the action of electrostatic field at substantially different temperatures at least one of which is substantially above two hundred and fifty degrees Fahrenheit, at each of which exist substantial differences in electrostatic susceptibilities in dry condition by reason .of which part of the separation may be effected, said temperatures being determined on the basis of differentiation in electrostatic susceptibilities in response to change in temperature and the differences in electrostatic susceptibilities being materially different at the different temperatures, including, subjecting said particles in dry condition to the action of, an electrostatic field while said particles are atone such temperature, and effecting a division of said particleson the basis of the electrostatic suscep- 'tibilities thereof at that temperature, and then subjecting a fraction of said particles the electrostatic susce'ptibilities whereof in dry condition at said one temperature were of the same crder of magnitude, in dry condition to the action of an electrostatic field while those particles are of the same chemical constituencies as when previously subjected but are at another such temperature. and effecting a division of those particles on the basis of the electrostatic susceptibilities thereof at that temperature.

24. The process of separating co-mingled particles of mineral material the electrostatic susceptibilities of which in dry condition at normal temperatures are of thesame order of magnitude, which comprises successive fractionations by successive subjections to the action of electrostatic field at substantially different temperatures each substantially different from normal temperatures, at each of which the chemical constituencies of the particles are the same as in dry condition at normal temperatures, but at each of which exist substantial difi'erences in electrostatic susceptibilities in dry condition by reason of which part of the separation may be efiected, said temperatures being determined on the basis of diiferentiation in electrostatic susceptibilities in response to change in temperature and the differences in electrostatic susceptibilities being materially different at the diflerent temperatures, including, subjecting said particles in dry condition to the action of an electrostatic field while said particles are at one such temperature, and efiecting a division of said particles on the basis of the electrostatic susceptibilities thereof at that temperature, and then subjecting a fraction of said particles the electrostatic susceptibilities whereof in dry condition at said one temperature were of the same order of magnitude, in dry condition to the action of an electrostatic field while those particles are of the same chemical constituencies as when previously subjected but are at another such temperature, and effecting a division of those particles on the basis of the electrostatic susceptibilities thereof at that temperature.

25. The process of separating co-mingled particles of refractory mineral material 'the electrostatic susceptibilities of which in dry condition at normal temperatures are of the same order of magnitude, which comprises successive fractionations by succ ssive subjections to the action of electrostatic eld at substantially different temperatures each substantially different from normal temperatures, at each of which the chemical constituencies of the particles are the same as in dry condition at normal temperatures, but at each of which exist substantial difierences in. electrostatic susceptibilities in dry condition by reason of which part of the separation may be efiected, said temperatures being determined on the basis of difierentiation in electrostatic susceptibilities in response to change in temperature and the differences in electrostatic susceptibili ties being materially different at the different temperatures; includi g, subjecting said particles in dry condition to the action of an electrostatic field while said particles are at one such temperature, and effecting a division of said particles on the basis of the electrostatic susceptibilities thereof at that temperature, and thensubjecting a fraction of said particles the electrostatic susceptibilities whereof in dry condition at said onetemperature were of the same order of magnitude, in dry' condition to the action of an electrostatic field while those particles are of the same chemical constituencies as when previously subjected but are at another such temperature,-and effecting a division of those particles on the basis of the electrostatic susceptibilities thereof at that temperature.

26. The process of separating co-mingled particles of zircon ore the electrostatic susceptibilities of which in dry condition at normal temperatures are of the same order of magnitude, which comprises successive fractionations by successive subjections to the action of electrostatic field at substantially different temperatures each substantially difierent from normal temperatures, at

'each of which the chemical constituencies of the particles are the same as in dry condition at normal temperatures, but at each of which exist substantial differences in electrostatic susceptibilities in dry condition by reason of'which part of the separation may be effected, said temperatures being determined .on the basis of differentiation in electrostatic susceptibilities in response to change in temperature and the difierences in electrostatic susceptibilities being materially different at the difierent temperatures, including, subjecting said particles in dry condition to the action of an electrostatic field while said particles are at one such temperature, and efiecting a division of said particles on the basis of the electrostatic susceptibilities thereof at that temperature, and then subjecting a fraction of said particles the electrostatic susceptibilities wlereof in dry condition at said one temperature were of the same order of magnitude, in dry condition to the action of an electrostatic field while those particles are of the same chemical constituencies as when previously subjected but are at another such temperature, and effecting a division of those particles on the basis of the electrostatic susceptibilities thereof at that temperature.

27. The process-of separating co-mingled particles of mineral material the electrostatic susceptibilities of which in dry condition at normal temperatures are of the same order of magnitude, which comprises successive fractionations by successive subjections to the action of electrostatic field at substantially different temperatures each substantially different from normal temperatures and at least one of which is substantially above two hundred and fifty degrees. Fahrenheit, at each of which the chemlcalconstituencies of the particles are the same as indry condition at normal temperatures, but at each of which exist substantial differences in electrostatic susceptibilities in dry condition by reason of which part of the separation may be effected, said temperatures being determined on the basis of differentiation in electrostatic susceptibilities in response to change in temperature and the differences in electrostatic.susceptibilities being materially different at the different temperatures, including, subjecting said particles in dry condition to the action of an electrostatic field while said particles are at one such temperature, and effecting a division of said particles on the basis of the electrostatic susceptibilities thereof at that temperature, and then subjecting a fraction of said particles the electrostatic susceptibilities whereof \in dry condition at said one temperature were of the same order of magnitude, in dry condition to the action of an electrostatic field while those particles are of the same chemical constituencies as when previously subjected but are at another such temperature, and eifecting a division of electrostatic susceptibilities in dry condition byreason of which part of the separation may be efiected, said temperatures being determined on the basis of differentiation in electrostatic susceptibilities in response to change in temperature and the difierences in electrostatic susceptibilities being materially diii'erent at the diiferent temperatures, including, subjecting said particles in dry condition to the action of an electrostatic field while said particles are at one such temperature, and effecting a division of said particles on the basis of the electrostatic susceptibilities thereof at that temperature, and then subjecting a fraction of said particles the electrostatic susceptibilities whereof in dry condition at said one temperature were of the same order of magnitude, in dry condition to the action of an electrostatic field while those particles are of the same chemical constituencies as when previously subjected but are at another such temperature, and effecting a division of those particles on the basis of the electrostatic susceptibilities thereof at that temperature.

EDWIN L. WIEGAND. I i 

